fix: 修复导航头组件返回图标名称错误

将返回按钮的图标名称从"rectLeft"更正为"left"，以匹配图标库中的正确命名

 <!--
  * @Date: 2026-01-29 21:09:28
  * @LastEditors: hookehuyr hookehuyr@gmail.com
- * @LastEditTime: 2026-01-29 21:18:14
+ * @LastEditTime: 2026-01-30 20:18:20
  * @FilePath: /manulife-weapp/src/components/NavHeader.vue
  * @Description: 通用导航头组件，用于页面顶部固定导航栏，展示页面标题。
 -->
@@ -12,7 +12,7 @@
   <div class="fixed top-0 left-0 z-50 w-full h-[250rpx] bg-gradient-to-b from-[#1E3A8A] to-[#2563EB] pt-[100rpx]">
     <div class="relative w-full h-full flex items-center justify-center px-[32rpx]">
       <div v-if="canGoBack" class="absolute left-[32rpx] flex items-center justify-center w-[60rpx] h-[60rpx]" @tap="goBack">
-        <IconFont name="rectLeft" size="18" color="#fff" />
+        <IconFont name="left" size="18" color="#fff" />
       </div>
       <span class="text-white text-[35rpx] font-normal">{{ title }}</span>
     </div>